Concert Lead and 6x12 cab, need your help please!

[lofiandicons]

Hello fellow amplifier worshippers - I have a black face/red knob Sunn Concert Lead head, one channel, two inputs (bright and normal) and a 6x12 cabinet with the silver grill cloth.  5 of the 6 speakers in the cabinet are originals.  I've read these 6x12 s have 6ohm rated speakers, I've also read they're 12 ohm rated?  I've seen the head rated @ 200W @ 2ohms and @ 100W @ 4 ohms.  The head isn't so much of a concern, I'm never running a 2 ohm load and I'm not trying to, but does anyone know for sure what the original speakers in the 6x12 cabinets were rated?  I'm resigned to the fact I probably won't be able to find the oddball 6 ohm or 12 ohm 12" speaker I need but I'm wondering what these really are so I can figure out (without a multimeter right now) what speaker to use to replace the missing original or if I should replace the missing original and another one of the originals to reduce the chance of any weird phasing/air pressure/etc etc etc issues.  I've searched around on the web and the info I did find on this topic read like greek to me.  If anyone can help with information and explanation in layman's terms I'd be really grateful.  Thanks everyone.

[gtrplayr1976]

I had a 6x12 ,and ran it at 8 ohms with my Model T.  My cab was 6 ohm.

[lofiandicons]

thanks for your reply.  I've read that those 6x12s are rated @ 6 ohms for the cab, so I wasn't concerned running the concert lead head into it since the head is 4 ohms.  but i wanna replace that missing original speaker and I'm not sure whether to put a 4, 8 or 16 in there.  Furthermore, maybe I should actually replace two of the originals (the missing one and one of the 5 still in there) to spread the load around more evenly?  I've been using this : http://www.colomar.com/Shavano/impedance_proc.php to try and help me figure this out but trial and error isn't getting me very far.  Was hoping someone on here owned the same rig as me and could give me some insights for getting this cabinet back to full force, or at least as best as modern speakers with moden ohmage ratings will allow.  I really wanna run this 6x12, for now I'm using the Concert lead to power an 8 ohm EV 1x15 cab and an Ampeg 8 ohm 4 x 12 cab in parallel so the ohm's for cabs and head match @ 4.  Moving and transporting isn't an issue (band has van) so it'd be nice to only have to drag one big cab instead of 2.  Anymore help or advice is appreciated.  Thanks everybody.

[gtrplayr1976]

I'd say take one of the originals and ohm it out.  I don't remember the impedance of the individual speakers, or the wiring configuration ,or we could figure it out.

[lofiandicons]

understood, don't have access right now to a multi meter so I'll have to put out a call with the band mates to see if anyone has got one.  In the meantime, if anyone owns this rig or knows the specs and could forward the info along I'd be very appreciative.  Thanks.

[gtrplayr1976]

Here's a little more info I found.  Unless it has been changed, each pair of transducers is wired in series, then the three pairs are wired in parallel, for a total of six ohms, mono. The two jacks are also in parallel, so you can daisy-chain another cabinet.
Do you have the slant ,or straight cab  (slant is actually slanted inside 3 on each side slanted inward )

after thinking about this, it would make sense to me if the speakers were 4ohm with each set wired in parallel = 2ohm, then the sets wired in series =6ohm  .  I'm not sure , just thinkin.

[Isaac]

First, which 6x12" cabinet is it? Is it the 30" wide cabinet from the 60's, or the 24" wide cabinet with the angled baffle from the 70's?

[lofiandicons]

Sorry for the long lull, just got back to town and regular use of the net.  It's the 24" wide cab with the angled baffle, 3 speakers a side slanted inward.

gtrplayr1976 - what you're saying makes sense but almost everywhere I've looked i've read that the original speakers have an odd ohm rating, either 6 or 12, debated by many.  I've been out of town so I didn't try using a multi meter on the original speakers, still have to track one down or just shell out the bucks for it.  If they were 6 ohm speakers, pairs wired in a series (12 ohms) and then three pairs in parallel (12/3) that would come out to a 4 ohm rating for the cab, which makes sense to me because its a 4 ohm head.  But, the jacks are in parallel so if you were to run two of the 6x12 cabs that'd be 4/2 for 2 ohms, which i've read the concert leads will handle but i would never do this, one 6x12 is plenty heavy and loud.  if they were 12, then it'd be series pairs (24) with three pairs in parallel (24/3) and comes out to an 8 ohm cab.  2 8ohm cabs in parallel would be 4 ohm total to match the head, but it seems less likely they'd match the head up for always running two of the 6x12 cabs.  I really need to check the ohms on the originals, because we could hypothesize wiring methods and ohms all day and still not know for sure.

Issac - 70's slanted baffle 6x12, perhaps you have the ohm answer I need?

Thank you both for the help thus far. 

[lofiandicons]

Also, please correct my math if anything is wrong, had this cab forever but just now trying to figure out how to replace the speaker and keep the cab ohm rating the same or as close as possible.

[loudthud]

Check the Master Parts List I scanned in this thread:

http://sunn.ampage.org/sdp/index.php/topic,5393.0.html

It lists the 81-0126-00-90 as the speaker for the 612 and says it is 8 ohms. The wiring is three branches each with a series connected pair. 16/3 = 5.33 ohms.

[Isaac]

loudthud, your information and math are both correct. However, Sunn, in its wisdom called the 612S a 6 ohm cabinet. Not much difference, when you get down to it.

[lofiandicons]

loudthud, your information and math are both correct. However, Sunn, in its wisdom called the 612S a 6 ohm cabinet. Not much difference, when you get down to it.

ah, many, many thanks to all three of you for the help.  That Master parts list is great, bookmarking that if needed for future reference.  Maybe I confused what I read elsewhere?  I thought I'd read the speakers themselves were 6 ohms each, but it makes sense that the cab is 6 ohms (5.34) with 8 ohm speakers, such a relief, getting an 8 ohm replacement won't really be any trouble.  So, what wattage do you guys recommend on this replacement 8ohm 12" speaker?  the Concert lead head is SS and is rated 100W @ 4 ohms.  I know the wattage of the cabinet is just the wattage of one of your speakers multiplied by how many speakers are in the cab (given they are all the same speakers).  So, lets say they are 25 watts each, so that'd be 150 watts for the cabinet.  But the wattage rating on the cabinet should be more than the wattage rating for the head, correct?  Because watts is power, so you want your cabinet to be able to handle as much power as the head will give?  Sorry for all the questions gentlemen, im 30 and been into music for over half my life, but recently, within the last year or so, I got tired of feeling totally ignorant when it came to the "math" behind heads and speakers and cabinets and I've been trying to educate myself.  So, again, thanks for all the help and advice, very much appreciated.     

[Isaac]

IIRC, the Concert Lead head is rated at 150W@4 ohms. Somewhat less at 5.33 (or 6) ohms. I wouldn't worry about the cabinet handling the power from the amp.